The present invention relates to apparatus for use in driving pipes or similar tubular structures, hereinafter referred to for convenience as pipes, into the ground.
Pipe or tube-driving apparatuses are used in the formation of underground pipe lines and tunnels and are installed in an underground excavation. Normally such apparatuses employ hydraulic piston and cylinder units which act on a thrust ring or member directly engageable with the end of the pipe to be driven. Since space is usually cramped a problem frequently encountered with such apparatus is to construct the apparatus to permit the units to drive in a pipe of somewhat greater length than the stroke of the units. This then involves several strokes or operative cycles of the units. In German patent specification No. 1634377 the units of a tube-driving apparatus can be changed over to alternately exert a pushing and then a pulling force on the thrust ring. In the pulling position the units are disposed at opposite sides of the pipe and are connected to the thrust ring with rods. In German specification No. 2241685 the units and thrust member are locatable inside the pipe, thereby saving considerable space, and hook-like locating members engage on the end of the pipe to transmit the thrust force thereto. Naturally this apparatus cannot be used with pipes of small cross-section. In German specification No. 1927870 the effective length of the piston rod of the ram or unit can be extended by a part lockable in various positions.
All these known forms of apparatus are generally quite costly and relatively complex and involve certain disadvantages during operation and a general object of this invention is to provide an improved form of apparatus.